Brake system.



PATENTED JAN. 2, 1906.

C. E. BARRY.

BRAKE SYSTEM.

APPLICATION FILED AUG. 13. 1903.

Inventor.

' Charles BBarfy I Htty.

Wvtnesses UNITED STATES PATENT OFFICE.

CHARLES E. BARRY, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

BRAKE SYSTEM.

Specification of Letters Patent.

- Patented Jan. 2, 1906.

To all whom, it may concern:

Be it known that I, CHARLES E. BARRY, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Brake Systems, of whichthe following is a specification.

My invention relates to improvements in air-brake systems, andparticularly in highspeed air-brake systems.

It is a well-established fact that the coefficient of friction is afunction of the speed and that when a train is moving at a high rate ofspeed more pressure may be brought to bear upon the brake-shoes withoutcausing the wheels to slide than when the train is moving at a lowspeed. Therefore if a high pressure be applied to the brake-shoes whilethe train is running at full speed and this pressure is graduallyreduced as the speed decreases, so that the wheels of the train aremaintained during the entire time of making a stop just on the point ofsliding, a maximum braking effect will be obtained. Heretofore it hasbeen proposed to bring about this gradual reduction of brake-shoepressure by providing a reducing-valve arranged to control anexhaust-passage leading from the brake-cylinder and operated to permitthe air to escape from the brake-cylinder at a rate proportional to theretardation of the train. The operation of such pressure-reducingvalves, however, is dependent upon the brake-cylinder pressure and thesize of the escape-opening, and these must be determined by experimentbased upon certain general assumptions of operation, which departconsiderably in many cases from the actual conditions, and therebydetract from the general efiiciency of the mechanism. In another type ofmechanism heretofore proposed the reduction of brake-shoe pressure ismade directly dependent upon the friction betweenthe brake-shoes and thewheels and is therefore free from the above objection and in operationmay be adjusted so that the reduction of brake-shoe pressure is broughtabout only when the friction between the brake-shoes and the wheelsreaches a point beyond which it cannot go without causing the wheels toslide.

My invention relates to the latter type of mechanism; and it consists ina novel arrangement of the pressure-controlling mechanism whereby thereduction of pressure on the brake-shoe is stopped when the pressure hasreached a limit at which skidding the wheels is impossible for anyspeed.

My invention comprises certain other novel features which will bespecifically pointed out in the following specification and appendedclaims.

I have shown one embodiment of my in vention in connection with anautomatic airbrake system in the accompanying drawings, in which Figure1 is a side elevation of a portion of a car truck equipped withmechanism embodying the features of my invention. Fig. 2 is a plan of aportion of said truck and said mechanism. Fig. 3 is an enlarged view ofa portion of said mechanism, illustrating the exhaust controlling valvecasing and the spring-holding stirrup in section. Fig. 4 is a rearelevation of that portion of the mechanism shown in Fig. 3 with aportion of the controlling-valve casing broken away so as to show theinlet and outlet ports, and Fig. 5 is a diagram illustrating theconnections of said -mechanism with the other parts of the brake system.

In the drawings, designates the casing of the exhaust-controlling valve,which is mounted on the horizontal portion of an angle-bar 11, whichforms one of the cross members of a car-truck 12. This valvecasing 10 isprovided with an inlet or supply port 13 and exhaust-ports 14 15 and aslidevalve 1 6, which normally closes the inlet-port 13. The stem 17 ofthe slide-valve extends down through an opening in the angle-bar 1 1 andis movably secured at its lower end by means of pins 18 and 19 to thelower horizontal portion of a Z-shaped lever 20. This lever 20 ispivotally secured near its upper end at the point 21 to a casting 22,which is bolted to the vertical portion of the cross-bar 11 in proximityto the valve-casing 10. This Z-shaped lever, together with the down-'wardly-extending links 23 and 24, pivotally secured to its upper andinner end, constitute the connecting-lever mechanism between thevalve-piston and the brake-shoe, the lower end of the links 23 24 beingsecured to the brake-shoe head 25. The head 25 is provided with theusual brake-shoe 26 and through the agency of the usual cross-bar 27 andbrake-rigging 28 operates to apply pressure to the brake-shoe when thebrake-cylinder is charged. A stirrup 29 is secured to the cross-bar 11directly beneath the valve casing and serves both as a guide for thelower horizontal portion of the lever -and as a casing for coiledsprings 31, which bear upon opposite sides of this portion of the lever20 and normally maintain it and the valve 16 in a central position.Suitable stops 32 on the inner walls of the stirrup limit the movementsof the lever 20.

The supply-port 13 of the valve-casing 10 is in direct communicationthrough a flexible connection 33 with a pressure-retaining valve 34, andthe latter is connected in turn by a pipe 35 with the upper end of thebrakecylinder 36. This brake-cylinder is associated with the usualauxiliary reservoir 37 and triple valve 38 of an automatic air-brakesystem. As clearly illustrated in Fig. .3, the ports of thepressure-retaining valve are so disposed that unless the pressure abovethe piston is sufficient to overcome the upward pressure of the springcommunication cannot be established between the brake-cylinder and thecontrolling-valve 10. In the practice of my invention the spring of theretaining-valve should be adjusted so as to cut off communication withthe controllingvalve, and thereby render it inoperative whenever thebrake-cylinder pressure falls to a point which can be used throughoutthe remainder of the stop without causing the wheels to slide.

In'the operation of the mechanism herein disclosed, assuming that thetrain is traveling at full speed and it is desired to make a stop, assoon as the triple-valve 38 is actuated by a reduction in train-pipepressure to admit a high pressure from the auxiliary reservoir 37 to thebrake-cylinder air at this high pressure will flow through theconnection 35 and force down the piston of the retaining-valve 34, andthus establish communication with the controlling-valve 10. At theinstant this high pressure is applied to the brake-shoes the movableparts of the mechanism will be in the position illustrated in Figs. 3and 4that is, the valve 16 will close the inlet-port 13and no air willbe allowed to escape from the brake-cylinder. However, as soon as thespeed of the train decreases by reason of the brake action the frictionbetween the shoe 26 and its wheel will increase and when it hasincreased sufficiently to drag the shoe in the direction of rotation ofthe wheel in opposition to the restraining action of the springs 30 and31 the valve 16 will uncover the inlet-port and es tablish communicationbetween it and one of the exhaustports 14 15, according to the directionof rotation of the wheel, and air will then escape from thebrake-cylinder, and thereby through the agency of the brake-riggingcorrespondingly reduce the brakeshoe pressure. As soon as thisbrake-shoe pressure falls off so that the friction between thebrake-shoe and its wheel is insufficient to pull the brake-shoe aroundin opposition to the springs 30 and 31 the parts will be returned tonormal position through the action of said springs and the inlet-port 13of the controlling-valve closed. Upon further reductions in the speed ofthe train the same operation of the parts will be repeatedintermittently until the pressure in the brake-cylinder has fallen offsufficiently to allow the retainingvalve 34 to cut off communicationbetween the brake-cylinder and the controllingwalve, and thereby renderthe controlling-valve inoperative, and, as previously indicated, theretaining-valve should be adjusted so as to bring this about when thepressure in the brake-cylinder has fallen sufficiently to render furtherreductions unnecessary.

It is of course apparent that many alterations and modifications may bemade in the mechanism herein disclosed without departing from the spiritand scope of my invention, and I therefore do not wish to be limited tothe specific mechanism shown, but aim to cover by the terms of theappended claims all such alterations and modifications.

What I claim as new, anddesire to secure by Letters Patent of the UnitedStates, is

1. In an air-brake system, a brake-shoe, a brake-cylinder controllingsaid shoe, a passage from said cylinder to atmosphere, a valvecontrolling said passage, operative connections between said valve andsaid brakeshoe, and means for rendering said valve inoperative when thepressure in said cylinder is below a definite value.

2. In an air-brake system, a brake-shoe associated with a wheel of thevehicle, a brake-cylinder controlling said shoe, an exhaust-passage fromsaid cylinder to atmosphere, a valve in said passage, operativeconnections betweensaid brake-shoe and said valve whereby said valve ismoved to open said passage when the friction between said shoe and thewheel exceeds a definite amount, and means independent of said valve forclosing said passage when the pressure in said cylinder is below adefinite value.

3. In an air-brake system, the combination with the wheels of a vehicleto which the system is applied, of a plurality of brakeshoes associatedtherewith, a brake-cylinder and brake-rigging by which pressure may beapplied to said shoes, a valve controlling an exhaust-passage from saidbrake-cylinder, means connected to one of said brake-shoes and operablethereby when the friction between it and its wheel exceeds a definiteamount to exhaust said brake-cylinder, and means for cutting off saidexhaust when the brake-cylinder pressure falls to a definite point.

4. In an air-brake system, the combination with a car-truck, brake-shoesand rigtion of a brake-cylinder, a valve arranged to control anexhaust-passage leading from said cylinder, a pressure-retaining valvelocated in said passage, a brake-shoe associated with one of the wheelsof the vehicle, and means operated by said shoe to actuate saidcontrolling-valve.

In Witness whereof I have hereunto set my hand this 12th day of August,1903.

CHARLES E. BARRY. Witnesses:

BENJAMIN B. HULL, HELEN ORFORDf

